If one has the Player's Handbook, Xanathar's Guide, and the Essentials Kit, how necessary is the DMG to homebrewing campaign material?

I'm looking for detailed responses as to what the DMG offers that cannot be easily found via DNDBeyond basic or whipped up via homebrew rules and the above books as a guideline.

Let's see. I would have to say the largest benefits of the DMG are (in no particular order other than when I think of them):

• Probably the only source of info on outer planes in 5e (but only a whopping paragraph or 2 per plane).
• General DM tips (how to world build, plan encounters, NPCs, etc. This part is the majority of the book.)
• Downtime activities
• A large list of magic items and other rewards for quests (including several rollable tables for random loot).
• A small handful of rules not in the PHB. (Skill DCs, diseases, etc)
• A rather extensive walkthrough on how to homebrew and balance monsters, spells, and items.

Hmmmm...well, that sounds to me like, aside from the list of magic items and info on the outer planes, I'm not missing much.  Downtime,  skill DCs, and balancing spells and monsters can all be handled via DDB forums, from what I've seen.  

Thanks.